Circuit Description

ECT sensor uses a thermistor to control signal voltage to PCM. PCM applies and monitors 5-volt reference signal to sensor. When engine coolant is cold, sensor (thermistor) resistance is high and PCM will sense a high signal voltage. As engine coolant warms, sensor resistance becomes less and PCM voltage drops.

Code P1115 will set when the following conditions are present.

• PCM indicates ECT sensor signal voltage is high (greater than 4.8 volts) for 30 seconds.